TWO-FREQUENCY TYPE ULTRASONIC VEHICLE DETECTOR

PURPOSE:To obtain a device which has superior wear resistance and durability while transmitting and receiving ultrasonic waves having two frequencies, by using the oscillator formed by providing a radiating tool to the base oscillator of an electrostrictive oscillator. CONSTITUTION:The oscillator formed by providing the base oscillator of an electrostrictive oscillator is used for an ultrasonic transmitter and receiver. For example, the electrostrictive oscillator 10 includes the base oscillator which is the connection body of ceramic 11 and a metallic plate 12, and a horn-shaped radiating tool is provided at the broken-line position of the base oscillator. Then the electrostrictive oscillator 10 is mounted on the substrate 15 in a conical horn 14 for obtaining priper directivity and is connected to a cable 17 by a plug 18. The rear surface of the horn 14 protects the oscillator 10 and an electric connection part and is covered with a horn cover 16. The respective constituent parts can be formed of rubber and plastics, so the weight is reduced, no movable part is provided, and a magnetic field is unnecessary, thereby obtaining the device free of the influence of dust, etc.